This is a homework question; I'm supposed to use power series to find the following sum: ∞∑n=1n2n
I took the geometric series 11−x=∞∑n=0xn
and differentiated and multiplied both sides by x to get x(1−x)2=∞∑n=1nxn
I'm stuck because I'm not sure how to make the 12n
term appear.
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